Optical wireless communications (OWC) are high-speed and highly secure communication technologies that are developed to support radio frequency solutions, which face today the rapid growth of wireless data exchanges. OWC usually employ PIN or avalanche photodiodes for optical reception. However, despite their numerous advantages, these photoreceivers have a low level of sensitivity, which limits the communication coverage to a few square meters and can only be improved at the expense of the compactness and power consumption of the OWC system, whereas reducing these two parameters is actually key for OWC to enter consumer equipment such as smartphones or computers.

A very promising solution is to use instead more sensitive photoreceivers such as single photon avalanche diodes (SPADs), as these are able to detect light at the photon level and are compatible with CMOS technology, so that high-speed and high sensitivity OWC receivers in the form of specific integrated circuits (IC) may be built. Although SPADs suffer from several limitations (limited photon detection efficiency, dead time, etc.), the literature has shown they can be used in OWC systems for Gbps links. However, existing works are mainly theoretical and the few experimental results available use commercial SPADs not optimized for OWC and evaluated according to a limited number of metrics.

The CLIPS project thus aims to demonstrate the full potential of SPADs for OWC by adopting the following global optimization approach (from technology to system): 1) Design a 3D IC receiver at 940 nm to benefit from the latest advances in 3D SPADs on silicon, initially developed for proximity detection, etc. 2) Integrate this receiver into a complete OWC system, whose performance will be evaluated according to multiple key performance indicators and in nominal use cases. To that end, the CLIPS project brings together leading-edge organization in OWC (Oledcomm, LISV) and in the development of SPAD IC (INL, ICube, TIMA).

Illustration created by ChatGPT on December 7, 2024.